A subcutaneous injection is a method of administering medication. Subcutaneous means under the skin. In this type of injection, a short needle is used to inject a drug into the tissue layer between the skin and the muscle. Medication given this way is usually absorbed more slowly than if injected into a vein, sometimes over a period of 24 hours.
This type of injection is used when other methods of administration might be less effective. For example, some medications cannot be given by mouth because acid and enzymes in the stomach would destroy them. Other methods, like intravenous injection, can be difficult and costly. For small amounts of delicate drugs, subcutaneous injection can be a useful, safe and convenient method of getting a medication into your body.
Medications administered by subcutaneous injection include drugs that can be given in small volumes (less than 2 mL). Insulin and some hormones are commonly administered as subcutaneous injections.
Other drugs that need to be given very quickly can also be administered via subcutaneous injection. Epinephrine comes in an automated injector or “EpiPen” form that is used to quickly treat severe allergic reactions. Some pain medications like morphine and hydromorphone can be given this way as well. Drugs that prevent nausea and vomiting like metoclopramide or dexamethasone can also be given via subcutaneous injection.
Some vaccines and allergy shots are administered as a subcutaneous injection. Many other vaccines are administered as an intramuscular injection (into muscle tissue rather than subcutaneously).
The location of injection is important for subcutaneous injections. The drug needs to be injected into the fatty tissue just below the skin. Some areas of the body have a more easily accessible layer of tissue, where a needle injected under the skin will not hit muscle, bone, or blood vessels.
The most common injection sites are:
- Abdomen: at or under the level of the belly button, about two inches away from the navel
- Arm: back or side of the upper arm
- Thigh: front of the thigh
Equipment used for subcutaneous injections includes:
- Medication: Vials of liquid medication can be single-use or multi-use. Vials can also be filled with a powder to which liquid needs to be added.
- Syringes: Syringes with short 5/8-inch-long needles. The thickness of the needle is usually 25 or 27 gauge. There may be other options for doses more than 1 mL or for children or visually impaired patients.
- Auto-injector pen: Some medications are available in a “pen” with a short single-use needle screwed onto the end of a pen-shaped, multi-use vial. The amount of medication needed is then dialed in at the end. As mentioned earlier, emergency medications like epinephrine can also come in a “pen” form.
1. Wash your hands. Wash your hands with soap and warm water to prevent potential infection. Be sure to thoroughly scrub between fingers, on the backs of hands, and under fingernails. The Centers for Disease Control and Prevention (CDC) recommends lathering for 20 seconds – the time it takes to sing the “Happy Birthday” song twice.
2. Gather supplies. Assemble the following supplies:
- needle and syringe with medication or auto-injector pen
- alcohol pads
- puncture-resistant container to discard the used needles and syringe (typically a red, plastic “sharp’s container”)
3. Clean and inspect the injection site. Before injecting medication, inspect your skin to make sure there is no bruising, burns, swelling, hardness, or irritation in the area. Alternate injection sites to prevent damage to an area with repeated injections. Then you should clean the skin with an alcohol swab. Let the alcohol dry thoroughly before doing the injection.
4. Prepare the syringe with medication. Before withdrawing medication from a vial and injecting yourself or someone else, make sure you’re using the correct medication, at the correct dose, at the correct time, and in the right manner. Use a new needle and syringe with every injection.
Preparing a syringe:
Remove the cap from the vial. If the vial is multi-dose, make a note about when the vial was first opened. The rubber stopper should be cleaned with an alcohol swab.
Draw air into the syringe. Draw back the plunger to fill the syringe with air up to the dose that you will be injecting. This is done because the vial is a vacuum, and you need to add an equal amount of air to regulate the pressure. This makes it easier to draw the medication into the syringe. Don’t worry; if you forget this step, you can still get the medication out of the vial.
Insert air into the vial. Remove the cap from the needle and push the needle through the rubber stopper at the top of the vial. Inject all the air into the vial. Be careful to not touch the needle to keep it clean.
Withdraw the medication. Turn the vial and syringe upside down so the needle points upward. Then pull back on the plunger to withdraw the correct amount of medication.
Remove any air bubbles. Tap the syringe to push any bubbles to the top and gently depress the plunger to push the air bubbles out.
Preparing an auto-injector:
- If you are using a pen delivery system, attach the needle to the pen.
- The first time that you use the pen, you will need to prime it to push out extra air in the delivery system.
- Dial a small dose (usually 2 units or 0.02 mL, or as indicated by the package instructions) and push the button to expel the primer.
- Dial the correct dose and prepare for your injection.
5. Inject the medication.
Pinch your skin. Take a big pinch of skin between your thumb and index finger and hold it. (Your thumb and forefinger should be about an inch and a half apart.) This pulls the fatty tissue away from the muscle and makes the injection easier.
Inject the needle. Inject the needle into the pinched skin at a 90-degree angle. You should do this quickly, but without great force. If you have very little fat on your body, you may need to inject the needle at a 45-degree angle to the skin.
Insert the medication. Slowly push the plunger to inject the medication. You should inject the entire amount of medication.
Withdraw the needle. Let go of the pinched skin and withdraw the needle. Discard the used needle in a puncture-resistant sharp’s container.
Apply pressure to the site. Use gauze to apply light pressure to the injection site. If there is any bleeding, it should be very minor. You may notice a little bruising later. This is common and nothing to be concerned about.
If you’ll be doing this type of injection for more than one dose or for multiple days, you’ll need to rotate the injection sites. This means that you shouldn’t inject medicine into the same spot twice in a row. For example, if you injected medicine into your left thigh this morning, use your right thigh this afternoon. Using the same injection site over and over again can cause discomfort and even tissue damage.
As with any injection procedure, infection at the site of injection is a possibility. Signs of infection include severe pain, redness, swelling, warmth or drainage at the injection site. These symptoms should be reported to your physician immediately.